The acquisition of light scattering profiles as a function of angle is a critical part of certain measurement devices used in many laboratory and industry settings. Typically, particle sizing devices for laboratory use in the various scientific fields utilize the optical performance at the focal point of a spherical lens illuminated by a collimated light source. In such configurations, scattering from a plane-wave source by index of refraction variations into other angles of propagation in relation to the optical axis of the spherical lens is collected into annular rings with radii increasing with scattering angle. The scattering profile is deduced in a couple of different ways.
According to a first method, a linear detector is placed at the focal point of the spherical lens and is configured to detect the light scattering along a radius line of the annular ring pattern. This method often suffers from the lack of spatial extent of the detector to reduce noise through averaging.
According to another method, a linear detector array is placed at the focal point of the spherical lens and is configured to acquire the entire ring pattern from which ring intensities are calculated using digital signal analysis. This method often suffers from the high cost of signal processing computation power.
Thus, there is a need for a light scattering sensor that is capable of obtaining high resolution scattering profiles within reasonable acquisition times and with sufficiently low noise to allow the determination of scattering profiles in the presence of weak scattering. There is also a need for such a sensor to be available inexpensively for common applications in commercial products.